Studier av alkaliskt fosfatas och kollagen samt deras betydelse för skelettets mineralisering
There is convincing research which shows that the enzyme alkaline phosphatase (ALP) has a central role in the mineralization of bone, more precisely that its catalytic activity is needed in the process. ALP is found on the surface of matrix vesicles where the mineral is formed. One theory about the function of the enzyme is that it binds to fibrous collagen in the bone and thereby incorporating the mineral into the bone. The purpose of this study is to establish whether ALP binds to collagen. If this is the case, more elaborate studies around this will be performed. The strength of the binding between collagen and the different types of ALP will be evaluated, as well as on which part of the collagen the binding occurs. The binding is going to be studied by constructing a method for the ÄKTApurifier system. Initially, the pureness of the different type of collagens was determined by using SDS-PAGE and the activity of the different types of ALP was established. These were also compared with a native PAGE. In SDS-PAGE, bovine type I collagen showed markings for a triple helix, a double helix and two single strains, ?1 and ?2. Bovine type II collagen showed markings for a double helix and ?1-strains. Human type I collagen showed markings for a triple helix, two double helixes, two ?-strains and contaminations. Trials with collagen in Native PAGE did not provide any results. However, the trials with ALP revealed that the different types of ALP had different charge. Thereafter, blotting was performed. The results showed that all the different types of ALP, besides from E. coli, binds to bovine collagen type I and II and human collagen type I, however within various periods of time. In the trials with collagen coated plates the acquired results showed that some of the different types of ALP bind to collagen. ALP from liver binds the strongest to both collagen type I from rat and type IV from mouse. Intestinal ALP also binds to both types of collagen but not nearly as strong as liver ALP. Serum from rats did bind to collagen type I from rat but not to collagen type IV from mouse. ALP from kidney and human serum did not bind to either types of collagen. The trials concerning the ÄKTApurifier system were executed with ALP from liver alone because it had been proven to bind to bovine type I collagen through the previous methods. The results confirmed that ALP from liver binds to this type of collagen. The conclusions from this study are that ALP does indeed bind to collagen and does so to the triple helix and double helix form as well as the single strains of collagen. In other words the part of the structure in collagen that ALP binds to must exist in all three stages of collagen formation. Furthermore, it seems like some of the different types of ALP has a higher affinity for binding to collagen, as the time for binding to collagen varies for the different types of ALP. The results differed between methods concerning different types of ALP. Although, the method we consider to give the best result was blotting. However, the method using ÄKTApurifier can be complementary but needs further development.